Flue spark screen



Sept. 27, 1932. JOHNSON 1,879,289

FLUE SPARK SCREEN Filed April 18, 1952 Fig. I. F292 [ave/110v",

c/o/w. ,4. Johnson,

4f1orney6 Patented Sept. 27, 1932 UNITED STATES PATENT OFFICE JOHN A. JOHNSON, OF GRAWFORDSVILLE, INDIANA, ASSIGNOR TO NATIONAL SUPPLY AND SERVICE CORPORATION OF ORAWFORDSVILLE, INDIANA FLUE SPARK SCREEN Application filed April 18,

This invention relates to the art of spark arrestors adapted to be placed over the tops of flues or chimneys. In burning soft coal, much soot usually collects in the flue and smoke passages leading. from the furnaceto the flue and it is a frequent occurrence that this collected soot becomes ignited and burns with considerable intensity. As the soot burns, additional heat is thereby generated in the flue, and accordingly the flow of air through the flue rapidly increases and fans the burning soot with such force as to tear loose large flakes and particles of the soot and carry them up and out of the top of the flue with the result that there is present a great fire hazard particularly in the case of wood shingles being employed on the roof adjacent the chimney. These large burning chunks of soot continue to burn u'ntil consumed after dropping onto the roof. Also, it frequently occurs that papers and trash are to be burned, in which case, .pieces of burning paper will be lifted and carried up through the flu to blow about and drop back onto the roof adjacent the chimney.

If these large chunks of burning soot or scraps of burning paper or the like may be held back and prevented from discharging from the flue for a time interval until they are burned out or broken up, the firehazard would be greatly reduced. Tiny particles of burn ng soot escaping from ,the flue will either burn up or the combustion stop before they fall to the I'OOf,lOI even if they do fall to the roof while still burning, the heat gener ated by each particle is so limited and easily dissipated that the wood in contact therewith is not raised to the kindling temperature oy the time the combustion of the particle is completed or stopped by the cooling off of the isolated particle.

In forming a spark arrestor, it is necessary that any device applied to the flue must not interfere with the normal draft.

as applied to residence or low draft flu-es, has been that the devices would become clogged with soot or lined with paper scraps so that eventually. the flue draft would be so serious- 1y reduced as to require the removal of the 1k (llf- I ficulty heretofore encountered. particularly 1932. Serial N0. 606,040.

provide means for-arrestin the discharge of burning particles issuing rom a flue until the particles are consumed or broken up into small masses 'less than that normally required to ignite wood. An important object of the invention is not only to arrest such burnin particles as above indicated, but to brea up the larger particles and allow the smaller articles to escape without clogging up the evice to a point affecting the flue draft.

A still further important object of my in: vention is to provide a total efi'ective outlet opening which may never be reduced to less than that of the flue cross-section regardless of the amount of soot and the like leaving the flue. Other objects and advantages such as the extreme simplicity and relative low cost of production, willbecome apparent in thefollowing description of my invention as illustrated in the accompanying drawing, in which Fi 1 is a side elevation of. a device embodying my invention Fig. 2, an end elevation;

Fig. 3, a vertical transverse section on the line 33 in Fig. 1; and

Fig. 4, a fragmentary top plan view.

Like characters of reference indicate like parts in the several views in the drawing.

I form a: rectangular box 10 out of woven wire to be ertirely open across its under side but closed across itstop side. The center of the top 11 is preferably raised in the manner of a hip roof on a house. On each of the side and end walls of the box, I cut through the wire to form horizontally disposed slits one above the other and bend the wire inwardly from the top and bottom of the slits to form horizontally disposed openings 12 here shown as three in number in each wall, each opening opposing a like opening in the. opposite wall. By thus forming the openings 12, there is a short inwardly and downwardly sloping guard 13 above the opening and a similar inwardly and upwardly turned guard 14 below the opening. The inner edges of these guards terminate one above the other in substantially the same vertical plane. spaced inwardly from each wall and terminate with the rough, raw edges of the wires projecting along the top and bottom edges of the opening. A vertical slit 15 is cut at each end of the guards to permit the inward bending thereof and these slits 15 leave rough ends of the wiresprojeeting within the slit. These guards 13 and 14 extend to within the box but relatively short distances.

In the transverse plane including the lines of juncture of the guards 14 with the side walls of the box first above the lowermost openings, I position a screen 18 to extend entirely across the box from side to side and from'end to end. This screen 18 is fixed in position and has a much coarser mesh than that of the walls of the box. A second screen 19 is likewise fixed transversely aerossthe box above the second level of horizontal openings to be in the plane including the lines of juncture of the guards 14 of those second level openings with the side walls. This screen 19 is of a closer or finer mesh-than that of the screen 18 but coarser than that ofthe walls and top of the box, and also extends completely across the box between side and end walls. The box so'formed is placed to have its open under side across the flue opening and is there held in place by any suitable means, such as by Wires 20, Figs. 1 and 2, fixed to the box and to a chimney encircling wire 21.-

Now should the soot burn in the flue, large particles of the soot will tend to travel in the air current vertically upward to within the box, but will have such travel arrested by striking the transverse screen 18. This screen, having relatively large openings therethrough and the masses of sootstriking the screen with considerable violence, will Cause the masses of soot to be broken into smaller particles, if not stopped entirely, and these smaller particles will vtravel on through the screen 18 to in turn strike the next above screen 19 to again be broken into still smaller particles which pass on through'the screen 19 and strike the top 11 of the box 10, where the reduced particles must be broken up again in order to finally escape through the top. The draft through the flue will carry the major portion of the burning soot flakes or masses up against the screen 18 but there will be some of the flakes travel horizontally under the screen 18 toward the outer box walls and escape from the rapidly ascending central column of air. As those flakes travel any particles travel through the openings 12 between the inner ends of the guards 13 and 14, and should an occasional particle be carried toward the openings, in passing around over the edges of the guards, the larger particles will become impaled on the ragged ends of the inwardly directed wire (nds projecting from the guard edges so that the particles either hang there until burned up or break into smaller pieces before passing on outside of the box, and these smaller pieces are of no consequence as above indicated. The same screening and whirling action of soot particles occurs above the screens 18 and 9. The formation of the device is intended to brn-k up the larger particles into nonhazardous particles, and further to delay the passage of the particles from the flue through the device until the burning particles have been consumed or combustion has ceased by reason of the cooling down of the smaller particles to below the burning temperature.

During damp weather, soot may collect on the walls of the box to such an extent that air passage through the walls is completely stopped, but since the combined area of the openings 12 below the screen 19 is equivalent to or greater than the cross-sectional area of the flue, the normal draft of the flue is not aifected. Immediately the soot on the walls becomes dry it falls off, crumbles up and blows out through the walls. Rainwill also wash it ofl, and in the event of the burning out of the flue, it will burn off.

The transverse screens 18 and 19, while very effective on chimneys with strong or forced draft, may be omitted on chimnevs with weak or light draft. The use of the transverse screens wi therefore, depend largely upon the flue conditions encountered. The effective area of the openings 12 may be varied by changing the angles of the top and bottom guards 13 and 14 so that the openings may be adjusted as to efi'ective area for the particular fine on which the spark arrestor is to be used,

It is thus to be seen from the foregoing description that I have devised a spark screen or arrestor in which there is no tortuous passage for the flue current of air to follow around baflles or thelike and in which there is no possibility of clogging up to shut off the flue draft, and while I have shown and described my invention in the form as now best known to me, it is obvious that structural changes mag; be made therein without departing from t es irit of the invention, and I, therefore, inc ude equivalent forms within the scope of the invention as may be within the meaning of the following claims.

I claim:

1. A spark arrestor comprising a box open across its under side and having atop and fora-minous side walls and having a plurality of openings in its side walls, and guards disposed above and below each of the openings, one of said guards being above an opening to slo e downwardly and inwardly and another 0 said guards being below the opening to slope upwardly and inwardly, the in ner edges of the guards for each opening being spaced apart to define said opening.

2. A spark arrestor comprising a box with foraminous side walls open across its,under side and closed across the top and having a pluralit of openings in its side walls, and guards isposed above and below each of the openings, one of said guards being above an opening to slope downwardly and inward-- ly and another of said guards being-below the opening to slo e upwardly and inwardly, the inner edges 0 the guards for each opening being spaced apart to define said opening, and spikes projecting from the inner edges of said guards.

3. A spark arrestor comprising a box with foraminous side walls open across its under side and closed across the top and having a plurality of openings in its side walls, and guards disposed above and below each of the o enings, one of said guards being above an opening to slo e downwardly and inwardly and another 0 said guards being below the opening to slope upwardly and inwardly,

the inner edges of the guards for each opening being spaced apart to define said openin said 0 nin s bein 0 osite one an-' other in opposing walls of the box.

4. A spark arrestor comprising a box with foraminous side walls open across its under side and closed across the top and having a plurality of openings in its side walls, and

guards disposed above and below each of the openings, one of said guards being above an opening to slo e downwardly-and inwardly and another 0 said guards being below the opening to slope upwardly and inwardly, the inner edges of the guards for each opening bein spaced apart to define said open-- ing, sai openings being opposite one another in opposing walls of the box, and wires extending inwardly from the edges of said guards forming impaling spikes.

5. A spark arrestor comprising a box with foraminous side walls open across its under side and closed across the top and having a plurality of openings in itsiside walls, and

guards disposed above and below each of the openings, one of said guards bein above an opening to slope downwardly an inwardly and another of said guards being'below the opening to slope upwardly and inwardly, the inner edges of the guards for each opening being spaced apart to define saidopening, said openings being opposite one an-,

nous box open across its under side and .v

closed across the top and having a plurality of openings in its side walls, and guards disposed above and below each of the openings, one of said guards being above an opening to slope downwardly and inwardly and another of said guards being below the opening to slopeupwardly andinwardly, the in-' 'ner edges of the guards for each opening being spaced apart to define said opening, said openingsbeing op osite one another in opposing walls of thelm apart elevations, anda screen extending transversely acrossthe box above the first of said openings, said screen having openings therethrough greater than the openings through said box walls and top, and a second screen extending transversely across the box above the second elevation of said openings and having openings reduced in size from those of said first screen but larger than those throu h the box walls and top.

7. A spar screen comprising a box having foraminous side walls and having a plurality of openings in'the side walls, and a series of transverse screens joining the side walls within the box, each next above screen having openings therethrough reduced in size from the openings in the screen below.

8. A sparkscreen comprising a box'having foraminous side walls and having a plurality of openings in the side walls, and a series of transverse screen oining the side walls within the box, each next above screen having openings therethrough reduced in size from the openings in the screen below, an upper guard and a lower guard at each of said side ox, and located at spaced being spaced apart to define said opening, said openings being Opposite one another in opposing walls of the box, and located at spaced apart elevations, and a screen extending transversely across the box above the first of said openings, said screen having openings therethrough greater than the openings through said box walls, and inwardly extending spikes along the edges of said uards.

10. A spark arrestor comprising a oraminous box open across its under side and closed across the top and having a plurality of openings in its side walls, and guards disposed above and below each of the openings, one of said guards being above an openingto slope downwardly and inwardly and another of said guards being below the opening to slope upwardly and inwardly, the inner edges of the guards for each opening being spaced apart to define said opening, said openings being opposite one another in opposing walls of the box, and located at spaced apart elevations, and a screen extending transversely across the box above the first of said openings, said screen having openings therethrough greater than the openings through said box walls and top, and a second screen extending transversely across the box above the second elevation of said openings and having openings reduced in size from those of said first screen but larger than those through the box walls and top, and inwardly extending impaling spikes along the edges of said guards.

11. A spark arrestor comprising a box open across its under side and having a. top and foraminous side walls and having a plurality of openings in its side walls, and guards disposed above and below each of the openings, one of said guards being above an opening 7 to slope downwardly and inwardly and another of said guards being below the opening to slope upwardly and inwardly, the inner edges of the guards for each opening being ,spaced apart to define said openings, the slope v of said guards being varied to secure the desired efi'ective opening therebetween.

In testimony whereof I affix my signature.

JOHN A. JOHNSON. 

